leetCode_15_3Sum

题目描述

Given an array S of n integers, are there elements a, b, c in S such that a + b + c = 0? Find all unique triplets in the array which gives the sum of zero.

Note: The solution set must not contain duplicate triplets.

示例

For example, given array S = [-1, 0, 1, 2, -1, -4],
A solution set is:
[
[-1, 0, 1],
[-1, -1, 2]
]

代码实现

class Solution {
    public List<List<Integer>> threeSum(int[] nums) {
        List<List<Integer>> res = new LinkedList<>();
        Arrays.sort(nums);
        for (int i = 0; i < nums.length - 2; i++) {
            if (i == 0 ||(i > 0 && nums[i] != nums[i-1])) {
            int sum = 0 - nums[i];
            int left = i +1;
            int right = nums.length - 1;
            while (left < right) {
                if (nums[left] + nums[right] == sum) {
                    res.add(Arrays.asList(nums[i],nums[left],nums[right]));
                     while (left < right && (nums[left] == nums[left+1])) left++;
                     while (left < right &&(nums[right] == nums[right - 1])) right --;
                    left ++;
                    right --;
                } else if (nums[left] + nums[right] < sum) {
                    left ++;
                } else {
                    right--;
                }
            }
          }
        }
        return res;
    }
}